A British atomic clock is the most accurate measure of time in the world,
scientists have announced.

The machine, which is responsible for keeping Britain's clocks on track and also contributes to the international measure of time, is accurate to within two 10 million billionths of a second.

It is one of a handful of similar clocks which determine the exact length of a second by measuring microwaves as they cause reactions in atoms of caesium, a highly volatile element.

But a number of factors including the shape of the microwaves, the influence of nearby magnetic fields and even the clock's position above sea level can cause tiny shifts in its measurements.

By tinkering with the clock, physicists at the National Physical Laboratory (NPL) near London, led by Dr Krzysztof Szymaniec, were able to reduce its margin of error to unprecedented levels.

A new analysis of the clock, conducted by NPL scientists and American colleagues, published in the journal Metrologia, established that it will now drop just a billionth of a second every two months, making it the world's most accurate timekeeper.